Operator control device for an electrical appliance, and electrical appliance

ABSTRACT

An operator control device for a hob has a hob plate as an operator control panel, and a component carrier including conductor tracks and contact areas beneath the hob plate. A sensor element device including a sensor element housing is arranged on the component carrier, with electrically conductive material for forming a capacitive sensor element on a top face. In order to make electrical contact with the electrically conductive material on the component carrier, a spring element receptacle is provided in the sensor element housing, an electrically conductive spring element being inserted into the spring element receptacle, which electrically conductive spring element is composed of a material which is different from the electrically conductive material for the capacitive sensor element. The spring element, in the state in which it is inserted into the spring element receptacle, projects out of the spring element receptacle and establishes the electrical contact-connection under compression when the sensor element device is fastened to the component carrier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Application No. 10 2015 213 505.5, filed Jul. 17, 2015, the contents of which are hereby incorporated herein in its entirety by reference.

TECHNOLOGICAL FIELD

The invention relates to an operator control device for an electrical appliance, in particular for an electric hob, and also to an electrical appliance comprising an operator control device of this kind.

BACKGROUND

US 2014/0346022 A1 discloses an operator control device for a hob comprising a sensor element device in which sensor element housings are arranged on a component carrier beneath an operator control panel which is formed by the hob plate. In order to form capacitive sensor elements of the sensor element device, narrow elongate or round, tine-like projections which are composed of electrically conductive elastic material are provided on the top face of the sensor element housing. The projections bear firstly against the bottom face of the hob plate and in this way form capacitive sensor elements for a capacitive touch switch by operation with a finger which is placed over the capacitive touch switch on the top face of the hob plate. Electrical contact is made with the component carrier by means of sections of the electrically conductive elastic material which extend over the bottom face of the sensor element housing and which are pressed onto contact areas there. However, changes in material and therefore problems in making electrical contact may occur here in the event of operation over the long term, in particular with heating, this potentially leading to disturbances in functioning and even failure of the operator control device in the worst case.

BRIEF SUMMARY

The invention is based on the problem of providing an operator control device of the kind cited in the introductory part and also an electrical appliance of the kind cited in the introductory part, with which operator control device and electrical appliance problems which arise in the prior art can be solved and it is possible, in particular, to be able to produce an operator control device and an electrical appliance of this kind in a practical and highly functional manner.

This problem is solved by an operator control device and by an electrical appliance. Advantageous and preferred embodiments of the invention are the subject matter of the further claims and will be explained in greater detail in the text which follows. In the explanation, some of the features will be described only for the operator control device or only for the electrical appliance. However, irrespective of this, they are intended to be able to apply independently both to the operator control device and also to the electrical appliance. The wording of the claims is incorporated in the description by express reference.

It is provided that the operator control device has an operator control panel which advantageously can be closed at least in the region of the operator control device. This operator control panel can also be part of the rest of the electrical appliance, in particular in the case of a hob as the electrical appliance with a hob plate as the operator control panel. A component carrier, for example a printed circuit board, is arranged beneath the operator control panel. The component carrier has conductor tracks and contact areas for making electrical contact with components which are arranged on it. The component carrier is therefore at least largely a substantially conventional component carrier or a conventional printed circuit board. At least one of the components which is arranged on the component carrier is a sensor element device which has a sensor element housing which can be designed in a substantially block-like manner, and is advantageously flat and, in particular, substantially cuboidal. The sensor element housing has electrically conductive material which is advantageously elastic, in order to form a capacitive sensor element of the sensor element device for a touch switch. The electrically conductive material is arranged on a top face or on an upper region of the sensor element device or of the sensor element housing. In this case, the electrically conductive material advantageously bears against the bottom face of the operator control panel. The electrically conductive material can project beyond the top face of the sensor element device or of the sensor element housing, but does not necessarily have to do so. In at least one region of the sensor element housing, the electrically conductive material can be routed downward to a lower region of the sensor element device. However, this is purely optional; it is essential that the electrically conductive material is present on the top face or in the upper region.

According to the invention, it is provided that, in order to make electrical contact with the electrically conductive material on the component carrier or a control system which is arranged on the component carrier or is connected to the component carrier, a spring element receptacle is provided in the sensor element housing and/or in the component carrier, wherein an electrically conductive elastic spring element is inserted into this spring element receptacle. The spring element is advantageously designed in a different manner to or composed of a material which is different from the electrically conductive material for the capacitive sensor element. This spring element, in the state in which it is inserted into the spring element receptacle, can project out of the spring element receptacle, at least before the sensor element device has been fastened on the component carrier, and advantageously also thereafter. When the operator control device is assembled, that is to say when the sensor element device is fastened to or mounted on the component carrier, electrical contact is established by the spring element under compression of the spring element.

Therefore, the invention has the advantageous result that an electrically conductive elastic component, specifically the described spring element which is composed of a material which is different from that which is used for the capacitive sensor element, is used for making electrical contact with the sensor element device or the capacitive sensor element and therefore the electrically conductive material on the component carrier, which material forms the capacitive sensor element. The properties of the spring element can be matched primarily to this elastic or spring-action electrical contact-connection and therefore do not have to be the same as those for forming the capacitive sensor element. In particular, the material can be an electrically conductive elastic material which retains its elastic properties at relatively high temperatures as can occur, for example, beneath hobs during operation, that is to say up to 150° C. or even up to 180° C. This ensures permanent reliable electrical contact-connection even under temperature effects which would adversely affect the electrically conductive material for the capacitive sensor element.

The electrically conductive material for the capacitive sensor element is advantageously a thermoplastic elastomer (TPE), particularly advantageously which is based on silicone. The material can be extrusion-coated or injection-moulded onto the sensor element housing in a multi-component injection-moulding process.

In general, a spring element receptacle can be designed as an elongate channel; the longitudinal direction is particularly advantageously approximately at a right angle to the surface of the component carrier. In this way, an optimum spring action is achieved at least in the case of spring elements in the form of a body which is composed of elastic material, for example of electrically conductive plastic. The spring effect of the spring element can be utilized in an optimum manner owing to the orientation of the elongate channel.

A spring element receptacle for a spring element in the form of an elastic body is preferably cylindrical, in particular circular-cylindrical. Small projections, barbs or constrictions in cross section can be provided in order to hold an inserted spring element in the spring element receptacle.

In a first basic refinement of the invention, the spring element receptacle is provided in the sensor element housing, advantageously on the bottom face of the sensor element housing or at the bottom of the sensor element housing. The spring element receptacle can pass through the sensor element housing, but does not have to do so; it is only necessary for the spring element receptacle to be open at the bottom face, or the spring element can project out here.

The electrically conductive material of the sensor element housing can extend as far as the spring element receptacle, for example as an upper boundary, or even protrude into the spring element receptacle. An electrical contact-connection can therefore be established with the spring element by an adjoining contact. This contact should be made, as it were, with pressure applied in such a way that contact is not interrupted, even in the event of movements of one of the materials or relatively small dimensional changes. For this reason, it is considered to be particularly advantageous when the electrically conductive material projects into the spring element receptacle or, as an alternative, forms an upper stop or runs in the upper region of the spring element receptacle, for example also on the side. This ensures automatic contact and therefore electrical contact-connection between the electrically conductive material and the spring element when the spring element is inserted into the spring element receptacle and is pressed into the spring element receptacle or presses upwards in the spring element receptacle in particular when the operator control device is assembled.

In a further refinement of the invention, it is advantageous when the spring element projects out of the sensor element housing and in the process makes electrical contact with a contact area which is applied to the top face of the component carrier. In this way, the spring element can be, as it were, pressed onto the contact area, as is known from the prior art. A conductor track to a control system or evaluation system can then start from the contact area. In addition, it is possible to provide a means which improves the electrical connection, such as conductive paste or conductive adhesive, but this is not necessary. Further means can be a raised portion or a projection on the contact area, for example in the manner of an upwardly projecting nail or peg or pin. However, this is then more difficult to handle during mounting.

In a second basic refinement of the invention, the spring element receptacle is provided on or in the component carrier. Here, it is firstly possible for the spring element receptacle to be designed as a kind of bore or recess in the component carrier, a previously correspondingly described spring element being inserted into the bore or recess and advantageously being held therein in a captive manner. Electrical contact can be made at a bore of this kind, for example, by means of an electrically conductive inner wall of the bore which is then electrically connected to an abovementioned conductor track on the component carrier. This can be achieved using existing technology by way of copper-plating. In this case, the electrically conductive material on the sensor element housing can run as far as the bottom face of the sensor element housing or as far as a region which can be reached from below by the upwardly projecting spring element, in order to then establish an electrical contact in the finally mounted state by application. Therefore, a spring element of this kind can also be an elongate, for example cylindrical or circular-cylindrical, body which is composed of elastic and electrically conductive material, for example in foamed form, in this case too.

In an advantageous refinement of the invention, at least one spring element is provided as an electrical contact-connection for each capacitive sensor element. Precisely one spring element is particularly advantageously provided for each capacitive sensor element, that is to say for each coherent structure which is composed of electrically conductive material on the sensor element housing. A single electrical contact-connection for each sensor element is considered to be adequate. To this end, the spring element is electrically conductively connected to the capacitive sensor element or to the electrically conductive material of the capacitive sensor element.

In one refinement of the invention, the electrically conductive material runs on the sensor element housing at least partially in recesses, for example with a depth of a few mm, and is in particular injection-moulded therein. These recesses should be at least on a top face of the sensor element housing in order to form the capacitive sensor element here. A combination of coherent regions also runs advantageously at least partially in the sensor element housing, as a result of which better fastening is also possible. In particular, an electrical contact-connection to the spring-action element as contact element, that is to say in the direction of the spring element receptacle, can run in the sensor element housing.

In an advantageous refinement of the invention, all of the electrically conductive material, preferably the abovementioned TPE, is moulded onto the sensor element housing in one step. In a further step, it is possible to also injection-mould the spring element from a corresponding different material. However, in respect of the desired elastic and, respectively, spring-action properties, it is considered to be preferable to produce the spring element separately, in particular to also be able to foam the spring element to achieve the desired elasticity and then to insert the spring element.

In a further refinement of the invention, it is possible to provide light-permeable regions in the sensor element housing. At least some of the light-permeable regions can be provided close to the electrically conductive material or within regions around which the electrically conductive material runs. These light-permeable regions can be filled with light guide material in a manner which is known per se and in this case pass through the sensor element housing from bottom to top.

Yet further components, in particular an entire control system, of the hob can be arranged on the component carrier. A sensor element device advantageously has precisely one single capacitive sensor element and particularly advantageously also has only one single electrical contact-connection to a stated component carrier. A plurality of sensor element devices of this kind can be arranged on the component carrier of the operator control device, the sensor element devices also possibly each being of different design. At least two of these sensor element devices are then designed, as described above, with the electrically conductive spring element for making electrical contact.

As an alternative to an electrically conductive spring element for making electrical contact which is in the form of a plastic body, a metal spring, for example a helical spring or a leaf spring, can be used. A helical spring which is composed of metal material can especially be used similarly to an above-described electrically conductive spring element as an electrical contact on account of its substantially circular-cylindrical elongate outer shape. A metal helical spring of this kind can also be inserted into an elongate, channel-like spring element receptacle and can be pressed against the electrically conductive material for the capacitive sensor element and also against a contact area on the component carrier for the purpose of making electrical contact in each case.

An operator control device according to the invention can be installed in an electrical appliance according to the invention and in this case be pressed, in particular pressed with a spring action, against an operator control panel from below, wherein the operator control panel is part of an outer wall or side wall of the electrical appliance. To this end, the component carrier can be seated on a substrate or in a housing in a spring-mounted manner, wherein this housing can be directly or indirectly connected to the operator control panel to form one physical unit or as an electrical appliance. The electrical appliance is advantageously a hob and the operator control device is a part of the hob, wherein the operator control panel can be formed by a hob plate.

These and further features are apparent not only from the claims but also from the description and the drawings, where the individual features can in each case be realized on their own or jointly in the form of sub-combinations in an embodiment of the invention and in other fields and can constitute advantageous and inherently protectable embodiments for which protection is claimed here. The subdivision of the application into individual sections and sub-headings does not restrict the general validity of the statements made thereunder.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Exemplary embodiments of the invention are schematically illustrated in the drawings and will be explained in greater detail in the text which follows. In the drawings:

FIG. 1 shows an oblique view of a sensor element device according to the invention of an operator control device according to the invention;

FIG. 2 shows a side view of the sensor element device from FIG. 1 between a hob plate and a printed circuit board;

FIG. 3 shows a detail of a hob according to the invention in accordance with the assembled state of the components from FIG. 2;

FIG. 4 shows an oblique view of the sensor element device from FIG. 1 from below;

FIG. 5 shows a view of the sensor element device from FIG. 1 from below;

FIG. 6 shows an oblique sectional illustration A-A through the sensor element device from FIG. 4;

FIG. 7 shows a similar sectional illustration B-B to that in FIG. 6 with a sectional plane which is offset slightly to the rear; and

FIG. 8 shows a sectional illustration through an alternative refinement of an electrical contact-connection with the spring element held in a printed circuit board.

DETAILED DESCRIPTION

FIG. 1 shows an oblique view of a sensor element device 11 according to the invention with a block-like or cuboidal and substantially flat sensor element housing 13. The sensor element housing can be composed of plastic and produced using a plastic injection-moulding process, advantageously together with a plurality of other constituent parts. The sensor element housing 13 has a top face 15, visible here, and a bottom face 16, shown in the following figures. An above-described elastic thermoplastic elastomer or TPE is provided as the abovementioned electrically conductive material on the sensor element housing, in particular as TPE material 18 in appropriate tracks or channels. Here, the sensor element housing forms a kind of circumferential rectangular frame. TPE projections 19, which are intended to bear against a bottom face of an operator control panel in accordance with the abovementioned document US 2014/0346022 A1, are mounted or integrally formed on the frame. At the top left, the TPE material 18 merges with a TPE contact 21 which will be explained in detail below.

A so-called seven-segment display which is formed from a plurality of light guides 23 is located within the frame which is formed by the TPE material 18. The light guides are composed of light-distributing or diffuser material and can be inserted or injection-moulded into the sensor element housing 13.

In the side view in FIG. 2, the sensor element device 11 is illustrated with the sensor element housing 13 together with the top face 15 and the bottom face 16. This figure once again shows how the TPE projections 19 project upwards beyond the top face 15. A plurality of supporting feet 25 are integrally formed on the bottom face 16. A circular-cylindrical spring element 27 likewise projects at the bottom and will be explained in greater detail below.

A printed circuit board 30 as the component carrier cited in the introductory part is illustrated beneath the sensor element housing 13. By way of example, a contact area 31 with a conductor track 32 starting from it is provided on the top face of the printed circuit board 30 in a manner which is customary per se. The contact area 31 is advantageously round or lattice-like. Further contact areas and conductor tracks and primarily components such as, for example, a control system cited in the introductory part are advantageously present on the printed circuit board 30, but not illustrated here.

A hob plate 36 is illustrated at a certain distance above the sensor element housing 13. The hob plate rests on the sensor element housing 13 by way of its bottom face 38.

FIG. 3 shows a side view of how the hob plate 36 is mounted after the sensor element housing 13 is mounted onto the printed circuit board 30, the hob plate forming an operator control panel cited in the introductory part and therefore also being an integral constituent part of an operator control device 40 according to the invention here. Therefore, FIG. 3 also shows a detail of a hob 34 according to the invention, in which appropriate heating devices are further arranged at a different location below the hob plate 36. As a result of the sensor element housing 13 pressing against the bottom face 38 of the hob plate 36 as the operator control panel, the TPE projections 13 not only bear against the bottom face, but rather are pressed against it and also widened or pressed-flat to a certain extent. In a similar way, the printed circuit board 30 bears directly against the bottom face 16 of the sensor element housing 13, wherein the spring element 27 is pressed onto the contact area 31 and bears firmly against the contact area and also establishes a reliable electrical contact.

The TPE projections 19, possibly together with the TPE material 18 on the top face 15 of the sensor element housing 13, form a capacitive sensor element in a known manner by bearing against the bottom face 38 of the hob plate 36. An operator control operation can be identified and therefore a switching operation can be triggered by this capacitive sensor element in a known manner by placing a finger on a top face 37 of the hob plate 36 above the TPE projections 19 or above the sensor element housing 13. Electrical contact is then made at this capacitive sensor element by means of the TPE contact 21 to the electrically conductive spring element 27, the contact area 31 and the conductor track 32.

The oblique view in FIG. 4 of the bottom face 16 of the sensor element device 11 or of the sensor element housing 13 and the view in FIG. 5 from the bottom show the light guides 23, which light guides further have relatively large clearances above them here, the clearances then passing over SMD-LEDs on the printed circuit board 30. Above all, the spring element 27 projects from the bottom face 16, wherein it can project by, for example, 1 mm to 3 mm or even 5 mm beyond the bottom face 16 of the sensor element housing 13. The section lines for the sections A-A and B-B illustrated in FIGS. 6 and 7 are also indicated.

The oblique sectional illustration A-A of FIG. 6 through the sensor element housing 13 shows how the TPE material 18 is injection-moulded into a recess. In the region of the seven-segment display, the TPE material runs continuously, for example at a depth of 1 mm to 3 mm, in the sensor element housing 13. The TPE projections 19 project by approximately 1 mm to 2 mm.

The TPE contact 21 which consists of a kind of plate which is injection-moulded into a circular-cylindrical and elongate spring element receptacle 28 is shown on the left next to the TPE projections 19. The continuous electrical connection from the TPE contact 21 to the TPE material 18 or the TPE projections 19 is clearly shown.

A circular-cylindrical spring element 27 which is illustrated above the spring element receptacle 28 is inserted into the spring element receptacle. That side of the spring element 27 which faces the TPE contact 21, not illustrated here, bears against the spring element and establishes the electrical connection. In line with FIG. 2, the bottom face 27′ bears against the contact area 31 on the printed circuit board 30.

The spring element 27 is produced from electrically conductive material which is elastic, possibly both owing to its inherent material property and owing to its design, advantageously from a foamed material. By way of example, the material can be based on silicone or rubber, and graphite powder or metal powder can be added as an electrically conductive additive. Electrically conductive spring elements 27 of this kind are known in principle from the prior art, see EP 859467 A for example.

In the further sectional illustration of FIG. 7 according to section B-B which is approximately 1 mm to the rear in relation to sectional illustration A-A of FIG. 6, the spring element 27 is inserted into the spring element receptacle 28. Apart from that, FIG. 7 also further shows that the TPE material 18 is only partially visible owing to the somewhat offset sectional plane; in particular, the elongate section between the two TPE projections 19 of FIG. 6 is no longer contained in this section.

FIG. 7 also shows that the spring element 27 is compressed to a considerable extent, for example approximately 20% to 25%, when the bottom face 16 of the sensor element housing 13 bears on the top face of the printed circuit board 30. The material of the spring element 27 is generally selected such that it does not lose its elasticity on account of temperature effects and ageing, and therefore electrical contact is always ensured.

FIG. 8 shows a detail of an alternative operator control device 140 in which a spring element 127 is not held in a sensor element housing 113 similar to that from FIGS. 1 to 7, but rather on a printed circuit board 130. A hole 133 in the printed circuit board 130 forms the spring element receptacle according to the invention in this case, wherein this hole 133 can be copper-plated on the inside in a customary manner and is connected to a contact area surface which is provided on the top face around this hole 133. A conductor track, not illustrated, starts from the contact area surface. The spring element 127 has a tapered portion 127′ and a widened tip 127″ which adjoins the tapered portion, so that the spring element is inserted into the hole 133 in the printed circuit board 130 from above. Electrical contact is made by the tapered portion 127′ bearing against the inner wall of the hole 133 and against a contact area surface on the top face of the printed circuit board 130. The spring element 127 is firmly held on the printed circuit board 130 by the widened tip 127″.

The spring element 127 bears against a TPE contact 121 in the sensor element housing 113 by way of a top face and in this way establishes the electrical contact-connection. TPE material 118 starts from the TPE contact 121 and extends in the direction of a sensor element which is formed by the TPE material, for example in line with the above-described figures.

On the basis of FIG. 8, it is easy to imagine how, for example, a metal helical spring could be used instead of a spring element which consists of a solid body which is composed of electrically conductive and elastic material. In a similar way, a metal leaf spring or the like could also be provided, the metal leaf spring or the like being firmly soldered, for example, in a hole 133 in the printed circuit board 130 and a sensor element housing then being mounted onto the printed circuit board by means of the metal leaf spring or the like. In this case, the helical spring or leaf spring would then also again bear against a TPE contact or make electrical contact with the TPE contact. 

That which is claimed:
 1. An operator control device for an electrical appliance comprising: an operator control panel; a component carrier which is arranged beneath said operator control panel; said component carrier comprises conductor tracks and contact areas for making electrical contact with components being arranged on said component carrier; at least one of said components being arranged on said component carrier is a sensor element device comprising a sensor element housing, said sensor element device comprising electrically conductive material on said sensor element housing for forming a capacitive sensor element, wherein said electrically conductive material is arranged on a top face or on an upper region of said sensor element device, wherein in order to make electrical contact of said electrically conductive material to said component carrier, a spring element receptacle is provided in at least one of said sensor element housing and said component carrier; an electrically conductive spring element is inserted into said spring element receptacle; said electrically conductive spring element is composed of a material being different from said electrically conductive material for said capacitive sensor element; and said spring element, in a state in which said spring element is inserted into said spring element receptacle, projects out of said spring element receptacle in order to establish an electrical contact-connection under compression in an instance in which said sensor element device is fastened to said component carrier.
 2. The operator control device according to claim 1, wherein said spring element receptacle is an elongate channel.
 3. The operator control device according to claim 2, wherein said spring element receptacle is an elongate channel with a longitudinal direction at a right angle to said surface of said component carrier.
 4. The operator control device according to claim 1, wherein said spring element receptacle is cylindrical.
 5. The operator control device according to claim 1, wherein said spring element receptacle is provided in said sensor element housing.
 6. The operator control device according to claim 1, wherein said electrically conductive material on said sensor element housing extends as far as said spring element receptacle.
 7. The operator control device according to claim 6, wherein said electrically conductive material forms an upper stop of said spring element receptacle.
 8. The operator control device according to claim 6, wherein said electrically conductive material runs on a side in said upper region of said spring element receptacle.
 9. The operator control device according to claim 1, wherein said electrical contact of said spring element projecting out of said sensor element housing is made on said component carrier by means of a contact area being applied to said top face of said component carrier, wherein a conductor track is connected to said contact area.
 10. The operator control device according to claim 1, wherein said spring element receptacle is provided on said component carrier as a bore in said component carrier.
 11. The operator control device according to claim 10, wherein an inner wall of said bore is electrically conductive and is electrically conductively connected to one said conductor track on said component carrier.
 12. The operator control device according to claim 1, wherein at least one said spring element is provided for each said capacitive sensor element and is electrically conductively connected to said capacitive sensor element.
 13. The operator control device according to claim 1, wherein said spring element is composed of an electrically conductive and foamed flexible or elastic plastic.
 14. The operator control device according to claim 1, wherein said electrically conductive material on said sensor element housing runs at least partially in recesses in said sensor element housing.
 15. The operator control device according to claim 1, wherein said electrically conductive material runs in recesses on a top face of said sensor element housing.
 16. The operator control device according to claim 1, wherein light-permeable regions are provided in said sensor element housing, said light-permeable regions passing through said sensor element housing from bottom to top.
 17. The operator control device according to claim 16, wherein said light-permeable regions are filled with light guide material.
 18. An electrical appliance comprising an operator control device according to claim 1, wherein said operator control panel is part of an outer wall or side wall of said electrical appliance.
 19. The electrical appliance according to claim 18, wherein said electrical appliance comprises a hob and said operator control panel comprises a hob plate. 